1. Field of Invention
This invention relates to electronic packaging. Specifically, the present invention relates to systems and methods for packaging microprocessors with highdensity input/output connections in space limited applications.
2. Description of the Related Art
Integrated circuits having hundreds or thousands of input/output connections are used in a variety of demanding applications ranging from computer chips to telecommunications digital signal processors. Such applications typically require cost-effective and reliable integrated circuit packaging systems that can effectively accommodate large numbers of interconnections between integrated circuits or circuit boards. Efficient electronic packaging systems and methods for packaging integrated circuit chips are becoming increasingly important as integrated circuits become smaller and more complex.
A typical integrated circuit requires multiple input/output lines including power, ground, and signal lines. The lines are often directed to the periphery of the integrated circuit chip upon which the integrated circuit resides. Each line is connected to a separate bonding pad along the periphery of the integrated circuit chip to allow for wire bonding to other circuits in the system in which the integrated circuit is employed. However, space is limited along the one-dimensional edges of integrated circuit chips. The requirement for peripheral connections places design constraints on the integrated circuits, which may increase the cost of the circuits. In addition, in systems requiring multiple interconnected integrated circuit chips, the use of peripheral connections often dramatically increases the space required to accommodate the multiple chips, thereby increasing the size of the system. This is particularly problematic in applications such as cellular telephones and calculators where small circuit sizes are of paramount importance.
To overcome limitations with conventional peripheral circuit interconnection methods, methods that utilize the two-dimensional surface area of the integrated circuit chip are often employed. Such methods include ball grid array (BGA) and flip chip techniques. These connection methods typically involve the use of a substrate having several conductive bumps or balls that are connected to a circuit or array within or on the substrate. The array is designed to organize input/output lines into an appropriate pattern suitable for connection to other circuits in the system in which the integrated circuit is employed. The substrate is often placed beneath an integrated circuit chip. The integrated circuit chip has an integrated circuit on the top, and a pattern of contacts that extend through the integrated circuit chip to the bottom of the chip. The pattern of contacts coincides with the pattern of bumps on the associated flip chip or ball grid array. The flip chip is xe2x80x98flippedxe2x80x99 and aligned with the pattern of contacts on the underside of the integrated circuit.
Conventional packaging systems employing BGA or flip chip formats often have many drawbacks. For example, the BGA substrates often have low thermal conductivity. The low thermal conductivity decreases connection reliability due to differences in coefficients of thermal expansion between materials used for the balls and the integrated circuit contacts. The packaging systems often lack adaptability features that allow removal of integrated circuits and replacement with new integrated circuits with different contact patterns. As a result, the entire package is often discarded. In addition, due to design limitations inherent in a conventional BGA system, the packaging systems often have unnecessarily large footprints to minimize cross-talk between connections and accommodate high frequency operation.
Hence, a need exists in the art for a cost-effective and space-efficient packaging system and method for effectively accommodating integrated circuits requiring high-density interconnections to other circuits. There is a further need for a reliable packaging system that can withstand repeated temperature related stresses, can reliably accommodate high frequency signals, and that can be easily adjusted to accommodate new integrated circuits without requiring discarding of the electronic package.
The need in the art is addressed by the cost-effective electronics packaging system of the present invention. In the illustrative embodiment, the inventive system is adapted for use with an integrated circuits requiring ultra-high density input/output connections and includes a first circuit chip having a first pattern of contacts distributed across a surface area of the chip. The first pattern of contacts represents input/output connections. A three-dimensional circuit is disposed; spatially; parallel with respect to the first circuit chip for organizing the input/output connections into a second pattern of contacts suitable for connection to a second circuit.
In a specific embodiment, the three-dimensional circuit is a double sided DECAL. The double-sided DECAL includes a substrate having a first circuit pattern spatially parallel with a second circuit pattern on or in the substrate. The first and second circuit patterns are interconnected. The first circuit pattern has a third pattern of contacts coincident with the first pattern of contacts on the first circuit chip.
In the illustrative embodiment, the first circuit pattern and/or the second circuit pattern are ball grid arrays. The first circuit pattern and/or the second circuit pattern are coaxial connector grid arrays. The second circuit is disposed spatially parallel with respect to the three-dimensional circuit. The second circuit is a ceramic or laminate interposer that facilitates further organization of the input/output connections. The interposer includes a ball grid array or a coaxial connector grid array to facilitate the organization. A z-axis adhesive is disposed between the interposer and the three-dimensional circuit. A non-hermetic sealer disposed over the first circuit chip.